I'm not quite sure how to say this - it feels almost taboo in the hard-nosed world of cyber-journalism. Especially on a site known for the shark-like ferocity of its atheist readers. But here goes. I find Christmas so moving, and so beautiful. It's partly about getting a bit older, it's partly about having kids, but Christmas just gets more and more powerful.

Am I allowed to say this? I half-expect that the powers that be will block this little confession. One is welcome to whinge or joke about Christmas, or engage in yawny analysis of the multicultural issues raised - but is one still allowed to rejoice in its beauty?

I realised I was becoming more sensitive to Christmas a couple of years ago. I was listening to Desert Island Discs in the car, at some non-festive time of year. Someone (I think it was the gardener Monty Don) chose as one of his records a choirboy singing the opening solo of Once in Royal David's City. Of course I'd heard it a thousand times, but it hit me like it never had before: the piercing purity of it. It sounded like an utterance from another world, where innocence reigns. I seem to remember that my flinty worldly visage yielded a soft tear or two. Maybe a man has to reach a certain age before he can admit that he hears unparalleled beauty in a choirboy's voice, that all the struttings of rock-gods are crude noise in comparison.

I was emboldened to share such reflections by a recent article in which the atheist comedian Mark Thomas reflects on the power of carols. He is moved by Silent Night: "I love the way its melancholy sound swoops gently, searching for 'heavenly peace'." But the one that really gets him is Away in a Manger. He finds this carol, sung by children, so emotionally powerful that his atheism feels a bit shakier than usual: his loss of childhood faith suddenly feels like a loss.

I admire his honesty. Imagine what Dawkins would say: "Beauty and truth are utterly separate entities; atheists may appreciate the beauty of certain carols, just as they appreciate the beauty of certain Christian paintings, while dismissing the religious content." Indeed, Dawkins would doubtless call such songs dangerous, in their ability to inculcate superstition.

It's customary for atheists and agnostics to call the nativity story "a beautiful myth". What they mean is that the story is beautiful, but no more. It changes nothing; it is not really important; only the gullible could confuse its beauty with truth. It's beautiful but empty, inconsequential.

I think this position is deeply flawed. It won't do to call carols beautiful but meaningless. For their beauty is obviously related to their content. Their power derives from the particular story they tell: the birth of a baby which is also the arrival of total hope for the world, the triumph of good over evil, light over darkness. The beauty of this myth exceeds aesthetics. For its beauty is not neutral but is tied up in an assertion of value. To respond to this in strictly aesthetic terms is inadequate. And perhaps somewhat cowardly: it puts religion at arm's length by turning it into an aesthetic phenomenon.

Christmas seems to me the refutation of the idea that beauty and truth can be separated. The beauty of the Christmas story, and of the festival, is more than beauty. Mere aesthetics cannot account for it. This sort of beauty involves you, changes you, exerts a sort of authority over you, like the face of your beloved.

On another level I totally agree that the nativity story is a beautiful myth. GK Chesterton called Christianity "the true myth", and Christmas shows that its beauty is fundamental to its truth.